Thermocycler with a temperature control block driven in cycles

ABSTRACT

A thermocycler comprising a temperature control block ( 1,2,3 ) which is designed to receive several specimens and which is fitted with a control unit ( 6 ) that in consecutive cycles applies the different temperature levels (40° C., 70° C., 95° C.) of a PCR procedure to said block, said thermocycler being characterized in that said temperature controlling block is sub-divided into thermally separate segments ( 1, 2, 3 ) each of which is controlled separately and receives several specimens, the control unit ( 6 ) being designed to drive the said segments at different cycling rates (nine, seven, four).

[0001] The present invention relates to a thermocycler of the kind defined in the preamble of claim 1.

[0002] Thermocyclers have come to be part of the basic equipment of a molecular biology lab. They are used foremost to amplify nucleic acid stretches contained in a probe in low quantity using the Polymerase Chain Reaction (PCR) procedure.

[0003] In this procedure, the specimens are sequentially subjected to three temperatures in successive cycles, namely consecutively to the temperature of denaturation of about 95° C., then to the annealing temperature of about 40° C. and the elongation temperature of about 70° C. In some special cases two of theses temperature levels, that is the annealing temperature and the elongation temperature, also may be consolidated into one temperature level.

[0004] Before many specimens can be processed on a large scale, the appropriate PCR parameters must be determined to allow carrying out PCR using optimal parameters. It is known in this respect to vary both the temperatures at the particular levels and the reagent concentrations. Gradient cyclers are known to make temperature variation easier: these gradient cyclers apply different temperatures at different temperature levels to individual specimens.

[0005] It is known moreover that the number of cycles, i.e. the cycling rate, used in a particular PCR procedure may entail different results and hence it should be optimized. In the state of the art, however, optimizing the cycling rate is highly time-consuming because several passes each with a different cycling rate must be carried out consecutively in one thermocycler.

[0006] The objective of the present invention is to create a thermocycler allowing simplifying the optimization of the cycling rate.

[0007] This goal is attained by the features of claim 1.

[0008] The thermocycler of the present invention comprises several block segments operated by means of a control unit each at a different cycling rate. This design allows operating with several different cycling rates within the conventional range of such cycling rates, that is, illustratively between 10 and 30 cycles, in the individual block segments. This operation is economical in labor in that it takes place in one pass whereby specimens are made available in the various segments, said specimens being processed at different cycling rates. Obviously too, other different parameters may be employed at the same time in the particular segments for the different specimens, for instance different concentrations of reagents, in order that several parameters be simultaneously variable. Also the individual blocks may be designed as gradient blocks so that the particular level temperatures may be varied concurrently with the cycling rate.

[0009] The features of claim 2 are advantageous. This design simplifies the control unit. For instance the cycles may run in all segments simultaneously and synchronously and, each time, following the cycling rate prescribed for a given segment, the control function applied to this segment shall be terminated. Next, and preferably in the manner of claim 3, a cooling temperature is set in order that the specimens be preserved for subsequent analysis.

[0010] The present invention is shown in illustrative and schematic manner in the appended drawing.

[0011] The single FIG. 1 shows a thermocycler of the present invention and its related temperature functions.

[0012] In substantially schematic manner, FIG. 1 shows a top view of a thermocycler, its housing, cover and the like having been omitted. Solely the temperature control block is shown, which consists of three segments 1, 2 and 3 that, in the shown juxtaposition, are connected to one another by insulating layers 4.

[0013] Each segment 1, 2 and 3 is connected by a line 5 to a control unit 6 that may regulate them at the desired temperatures.

[0014] In the shown embodiment, the segments 1, 2 and 3 are identical and each is fitted with wells 7 in the form of recesses in a thermally conducting and illustratively metallic block, serving to receive specimens that may be filled directly into these wells 7 or may be contained in conventional plastic vials or be configured on in-situ slides for hybridization of which the shapes match the wells 7. In this illustrative embodiment of the present invention, the wells are configured in each segment 1, 2 and 3 as three rows and four columns.

[0015] In a manner not shown, the segments 1, 2 and 3 of the temperature-control block make contact on their underside away from the observer with appropriate temperature-control elements such as Peltier elements which, when appropriately driven by the control unit 6, may control the desired temperatures of the segments 1, 2 and 3 and for that purpose also may be switched from heating to cooling for instance by reversal of electric current.

[0016] In a manner not shown in the drawing, temperature sensors are mounted in the segments 1, 2 and 3 which through lines 5 that may be multi-wire cables feed data to the control unit 6 to enable said unit to accurately set the temperatures of the segments 1, 2 and 3.

[0017] A diagrammatic plot, where T denotes the temperature function of time t for the particular temperature which must be set at a given operational pass, is shown in FIG. 1 for each of, and below, the segments 1, 2 and 3.

[0018] In this illustrative embodiment, the control unit 6 is designed in such manner that it may apply four different temperatures to the segments 1, 2 and 3, namely a cooling temperature of 10° C., an annealing temperature of 40° C., an elongation temperature of 70° C. and a denaturing temperature of 95° C. The last three of said temperatures are consecutively applied in consecutive cycles in the way shown in the temperature plot near each segment.

[0019] In a first cycle, the temperature of each segment is initially raised to 95° C., then set to 40° C., then at 70° C., whereupon the first cycle is over. The next cycle again follows at 95° C., 40° C., 70° C. etc. FIG. 1 shows that a total of nine cycles are applied in the first segment 1. At the end of the ninth cycle, the temperature is lowered to the cooling temperature of 10° C. where it remains till the end of the operational pass.

[0020] As shown in the adjoining temperature plot, the same cycles are applied in the second segment 2, though they are fewer. Only seven cycles are applied. Thereupon the temperature is lowered to 10° C. As shown in FIG. 1, only four cycles are applied in FIG. 1.

[0021] In the shown, illustrative embodiment of the present invention, the cyclings of the three segments 1, 2 and 3 are synchronous and identical. The only difference is the cycling rate. Upon completing the predetermined number of cycles, and as shown in the temperature plot, cooling is applied in order to preserve the specimens against further heat effects.

[0022] Though not shown, the control unit 6 is fitted with adjustment elements by means of which the particular desired cycling rate can be adjusted for the individual segments 1, 2 and 3. Accordingly operation may be at different cycling rates, for instance at 10, 15 and 20 cycles. Moreover the same cycling rate may be used in all three segments.

[0023] In an alternative embodiment, the segments 1, 2 and 3 also may be in the form of gradient blocks that will apply somewhat different temperatures at one of the temperature levels, for instance at the temperature level of 70° C., to different wells 7 of one or all the segments. When using such a thermocycler, it will be possible to simultaneously vary in one operational pass both the cycling rate and the temperatures at one temperature level in order to determine the optimum of these two parameters. 

1. A thermocycler comprising a temperature controlling block (1, 2, 3) which is fitted to receive several specimens and which is driven by a control unit (6) in consecutive cycles to assume in a consecutive manner the different temperature levels (40° C., 70° C., 95° C.) of a PCR procedure, characterized in that the temperature controlling block is sub-divided into segments (1, 2, 3) each receiving several specimens and that are thermally separated and are controlled separately, the control unit (6) being designed to control the segments at different numbers of cycles (nine, seven, four).
 2. Thermocycler as claimed in claim 1, characterized in that the individual cycles in all segments are identical.
 3. Thermocycler as claimed in claim 1, characterized in that upon termination of their last cycle the segments (1, 2, 3) are controlled at a constant temperature (10° C.). 